When we saw jalapeño mashed potatoes on the menu at New York’s BLT Steak, we cocked an eyebrow, imagining something from an ill-conceived southwestern lunch buffet. But Laurent Tourondel didn’t build an empire of excellent steak houses by screwing up the sides. So we tried them. They were deliciously creamy, with a faint kick underneath the buttery Idaho-potato puree. The trick is using some fresh jalapeño for the bright complexity it affords, and some roasted jalapeño for that smoky depth of flavor.

Yields 2 quarts

**6 jalapeño peppers

1 tablespoon olive oil

1/3 cup cold water

Salt and pepper

2 cups kosher salt

5 pounds Idaho potatoes (about 4-5 large potatoes), scrubbed and

patted dry

1 cup butter, softened

2 cups heavy cream**

Preheat oven to 450 degrees. Halve three of the jalapeÃ±o peppers and carefully remove seeds. Rub the halved peppers with oil and place on a baking sheet. Roast in the oven for 8–10 minutes. While the peppers are cooking, halve the remaining raw jalapeÃ±o peppers and remove and discard seeds. Transfer both the roasted and raw peppers to a blender, add water, and puree until smooth. Season with salt and pepper and set aside.

Reduce oven temperature to 350 degrees. Evenly layer the kosher salt onto a rimmed baking sheet. Place the potatoes on top of the salt and bake for 60 minutes, until very tender when pierced with a knife.

Halve the potatoes lengthwise, and scoop the pulp into a mixing bowl. Pass the pulp through a food mill or a fine mesh strainer into a mixing bowl. Bring the butter and cream to a simmer in a medium sauce pot. Once the butter has melted, pour the liquid over the potatoes and, using a spatula, mix until incorporated.

Mix the jalapeño puree with the mashed potatoes until well combined. Season with salt and pepper.